The present invention relates generally to hybrid electric vehicle systems, and more particularly to a method and apparatus for interfacing between a magneto-resistive position sensor and a variable reluctance controller.
Variable reluctance (VR) engine crankshaft position sensors have been used in hybrid electric vehicles to determine positioning of a crankshaft and in turn aid in engine control timing. VR position sensors have been deemed unreliable due to stray magnetic fields from vehicle combined starter/alternator, which are located in a close proximity to the VR position sensors.
As a result Magneto-resistive (MR) position sensors have become widely used in hybrid electric vehicles. MR position sensors replace the use of VR position sensors in determining crankshaft positioning. Although, MR position sensors are less sensitive to stray magnetic fields, due to internal active digital circuitry rather than passive nature of VR position sensors, they are not compatible with VR type engine controllers. In other words VR type engine controllers are designed to receive a differential voltage from a VR position sensor. The output of a MR position sensor is a digital, usually 0 to 5 volt or 0 to 12 volt signal.
Currently in order to use a MR position sensor, an engine controller that is compatible with an MR position sensor is required, as to be able to interface with the MR position sensor. Hybrid electric vehicles that use a VR type engine controller are not compatible with MR position sensors. Therefore, in order for a hybrid electric vehicle to maintain using a VR type engine controller and switch from a VR position sensor to a MR position sensor, the controller needs to be redesigned or replaced by an engine controller that is MR position sensor compatible. Redesigning of an engine controller increases vehicle design costs as well as production costs.
There is a continuous effort to improve the functionality and cost of hybrid electric vehicles. Therefore, it would be desirable to provide a method of interfacing a MR position sensor with a VR engine crankshaft controller without redesign and reproduction of a VR type engine controller.
The foregoing and other advantages are provided by a method and apparatus for interfacing between a magneto-resistive position sensor and a variable reluctance controller. A position sensor and variable reluctance type controller interface circuit is provided. The circuit includes a position sensor having an output terminal and generating a position signal. A variable reluctance type controller, having an input bus, is electrically coupled to the position sensor via a voltage divider circuit. The voltage divider circuit supplies a voltage differential output signal in response to the position signal to the input bus.
A method of interfacing between the position sensor and the variable reluctance type controller is also provided. The method includes generating a position signal. A reference voltage on the variable reluctance type controller is divided to an approximately fixed voltage level. The approximately fixed voltage level is supplied to a negative input terminal on the variable reluctance type controller. The position signal is received on a positive input terminal of the variable reluctance type controller.
One of several advantages of the present invention is that it provides a technique for interfacing between a magneto-resistive position sensor and a variable reluctance type engine controller. Thereby, preventing the need for redesign of the variable reluctance type engine controller and therefore saving costs in redesign and production.
Another advantage of the present invention is that in being able to interface between a magneto-resistive position sensor and a variable reluctance type engine controller, a rotational position sensing system using these two components is more reliable than systems using variable reluctance position sensors.
The present invention itself, together with attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying figures.